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It has been about 20 years since I regularly worked on automotive A/C systems. BUT...if I remember correctly, when the a/c is off, the pressure equalizes until both sides are the same reading...that is why you can hear a "hissing" sound after running the a/c then when you shut the car down, a/c off, the freon gas travels back through the small orifice until the pressure is equal throughout the entire system. When you crank up & cut the a/c on, the compressor, which is basically a piston/pump (old style, any way...not sure on todays stuff) punps the freon through the system, forcing the freon through the tiny orifice valve...if there is not eniough freon, it'll read too low, too much freon or a blockage, too high...I can't remember the exact readings, but, (don't quote me...my memory isin't that good) on the high side, the average "good" reading would be around 150 to 180?? and, on the low side, around 30....??can't recall for sure. It is always best to have a high side pressure reading. When you put your hand on the low pressure linse, near the compressor or where it goes into the collector, does it feel cold at all? Does the high pressure line feel warm, or hot...this is normal.
Another thing, Back in Black is correct, a bad fan clutch can cause this, because the fan pulls air through the condensor when at idle...does it cool better travelling down the highway at 55 or 60...
You can try this...put a window fan infront of the grill, blowing air into the radiator/condensor, or, spray cool water from the garden hose over the condensor and see if it makes a noticable difference...has the car got a temp gauge or idiot light? If it has a temp gauge, have you noticed it running warmer than usual?
If the compressor is on the fritz, best get it replaced SOON because, if it blows, it'll send trash through the whole a/c system...then your looking at some bigger $$$ to repair. I would make sure they install a new accumulator if they replace the a/c comp. and, for what it's worth, spend the extra and get a whole new a/c compressor, not a rebuilt, they are more trouble than they are worth in the $$ you'll initially save. Some of those Fords had compressor problems, if it's a 1999, may very well be. Good luck, either way...I know I HAVE to have an a/c system that will FREEZE me out, or I can't breath in this freakin' heat here in SC.

Broke down and took the truck to Pep Boys. They did a diagnostics and found no leaks. Only the freon was overcharged so they let some out. The tech wrote on the report that is was cooling fine. However, when I hopped in the car for the ride home, it was still hot as balls. Dont get me wrong, its not heated air coming out, its just slightly cool, not as cold as it should be.

Would a bad blend door cause this. Essentially the heater would compete with the AC. Is there an easy way to check for a bad blend door.

I have a 90 day warranty on the AC diagnosis but their level of whats cool and mine are two different.

Possibly. Does it cool on MaxAC? On many Fords, but perhaps not all, using max AC renders the position of the blend door irrelevant because the heater water diverter valve is shut and no hot coolant can reach the core so there is no hot air to &quot;blend&quot; with. Yes, I had a similar issue...but it was not an Expy.Go to alldata and sign up. For 15 bucks you get access to more diagrams, diagnostic schemes, repair procedures etc than could ever use. They will have a detailed schematic of your system.